The Wave of the Future

Higher Waves Increase Erosion and Flooding Along the Oregon Coast

Think of the Oregon Coast and breathtaking images of craggy cliffs, idyllic seaside villages, and pounding surf come to mind. More than 200,000 people have made this picturesque landscape their home. And many times that number visit the coast each year.

Unfortunately, the trend of development creeping closer to the coast is clashing with another trend — increasing wave heights. Higher waves mean more coastal erosion and flooding.

“Increased development on borderline sites along the Oregon coastline puts homes and other stationary structures at risk,” says Patrick Corcoran, a coastal hazards outreach specialist with Oregon Sea Grant, one of NOAA’s National Sea Grant College Programs. “The ocean is becoming more dynamic. Winter wave heights, especially during storms, have been increasing over the past 30 to 50 years,” he explains.

A new NOAA-funded study, appearing in the journal Coastal Engineering this year documents this trend. Peter Ruggiero, an assistant professor at Oregon State University, led a a team of scientists from OSU and the Oregon Department of Geology and Mineral Industries. They found that while all waves off the Oregon Coast are taller on average than they were 35 years ago, the highest waves during winter storms are gaining height faster than the low waves of summer.

Big Breakers Causing More Damage than Sea-Level Rise

The effects from increasing wave heights and sea-level rise are similar — coastal erosion, flooding, and structural damage. However, the erosion caused by these bigger breakers, which crash ashore in November through March, is greater than the impact of the modest amount of sea-level rise currently affecting this coastline.

Global climate change also might be influencing wave heights, but Ruggiero and his team have not settled that question. Changes in storm tracks, higher winds, climate cycles, or other factors could be driving up wave heights too.

Monster Waves: A Very Real Threat

The researchers set out to recalculate the potential height of a massive, once-in-a-hundred-years wave. In the early 1990s, scientists thought, based on buoy data, that such a wave would be about 33 feet high. Then in 1997-98, the Oregon Coast experienced a series of waves 33 feet and higher. Those came during an El Niño year—when waters near the equator in the Pacific are warmer and waves higher.

“Data covering a period of more than 30 years now indicate that a 100-year wave could reach 46 feet or even higher,” says Ruggiero. Some local communities, like Neskowin, have installed walls of riprap, or loose broken stone, as a shield from the waves.

The riprap is a stop-gap measure while communities work to identify longer-term solutions. Oregon Sea Grant is playing a key role in bridging the research findings and community efforts to adapt to the changing environment.

NOAA Research Helps Communities Plan for the Future

To assess the effects of these large waves and sea-level rise on the coastline, Corcoran and Sea Grant colleagues are measuring the changing shoreline and assessing community vulnerability in light of a changing climate.

With this data, they are developing management tools and integrating the best available science into local decision making — focusing on Neskowin as a case community for adapting to the ongoing erosion problem.

The Oregon state Land Conservation and Development Department also is funding a pilot effort to draft a county hazards adaptation plan for Tillamook County where Neskowin is located. The NOAA Sea Grant work will generate invaluable information and hazard assessments for the adaptation plan.

“This is exciting to me because it applies Oregon State and NOAA research directly to a problem of pressing local concern,” says Corcoran. “It’s also exciting to see that so many partners are converging on this issue in this community at this time.”

Oregon Sea Grant is funded by NOAA through Oregon State University. Sea Grant is a nationwide network of 32 university-based programs that work with coastal communities. The National Sea Grant College Program engages this network of the nation’s top universities in conducting scientific research, education, training, and extension projects designed to foster science-based decisions about the use and conservation of our aquatic resources.